The structure of a conventional plasma display discharge tube (PDP) is roughly classified into a DC type PDP having a structure in which the metal surfaces of a plurality of electrode groups constituting an X-Y matrix are exposed to a discharge space and an AC type PDP having a structure in which the surfaces of X-Y matrix electrode group are covered with an insulating layer. There is also a hybrid PDP which is constituted by using the feature of each of the DC type PDP and the AC type PDP.
As a drive method of driving these PDPs by a memory operation, in the DC type PDP, there is a pulse memory scheme using a phenomenon in which a discharge cell which discharges once tends to easily discharge again because of the presence of metastable atoms and charged particles existing in a space.
As the AC type PDP, there is a wall-charge memory scheme which makes a re-discharge by using the difference between wall voltages generated by so-called wall charges, i.e., charged particles accumulated on insulating layers on the surfaces of X-Y electrodes.
In addition, although a conventional hybrid PDP (see Japanese Examined Patent Publication No. 7-70289) according to the invention of the present inventor uses a wall-charge memory scheme as shown in FIG. 1, the following method is employed. That is, after the changes generated by an address discharge due to the DC type X-Y matrix electrode are accumulated on a pair of memory sheet electrodes shared by all pixels as wall charges, a discharge is continued between both the memory sheet electrodes.
The memory sheet type PDP shown in FIG. 1 will be briefly described below. Referring to FIG. 1, a front glass plate is omitted. Anode electrodes 31 serving as a plurality of address electrodes and cathode electrodes 32 serving as a plurality of address electrodes which are arranged with a predetermined interval to cross one another are both DC type electrodes in which electrodes themselves are exposed to a gaseous space. The plurality of cathode electrodes 32 are adhesively formed on a back glass plate BGP by a method such as printing or the like. The plurality of anode electrodes 31 are transparent electrodes which are adhesively formed on a front glass plate.
Memory sheets 33 and 34 serving as AC type electrodes which are covered with an insulating layer are located between the plurality of anode electrodes 31 and the plurality of cathode electrodes 32 to be opposed to each other. The memory sheets 33 and 34 are formed such that metal plates are etched to have grating-like shapes, and all the surfaces thereof including the inner walls of the through holes are covered with an insulating layers.
The plurality of anode electrodes 31 and the plurality of cathode electrodes 32 are arranged such that the crossing portions of these electrodes correspond to the through holes of the memory sheets 33 and 34, respectively.
Space charges generated by discharges of pixels arranged at the crossing portions between the plurality of address electrodes 31 and 32 crossing each other are accumulated on the wall surfaces in the through holes of the memory sheets 33 and 34 as wall charges. An AC pulse voltage is applied between both the memory sheets 33 and 34 by the using the wall changes, thereby performing a continuous memory discharge display.
Another hybrid PDP (see Japanese Examined Patent Publication No. 3-50378) according to the invention of the present inventor, as shown in FIG. 2, has a DC type X-Y matrix and an AC electrode called a single trigger electrode which is common to both the whole surfaces. The trigger electrode has only a so-called trigger operation for assisting the discharge of the DC type PDP to rise, but has no memory function. As the trigger electrode, for example, a metal mesh-like electrode having the same structure as that of the memory sheet described above can also be used. However, this electrode has a structure which can perform a trigger operation but is not sufficient to perform a memory operation. In addition, a proper memory drive method has not been invented.
The PDP using the trigger scheme shown in FIG. 2 will be briefly described below. A plurality of anode electrodes 41 and a plurality of cathode electrodes 42 which are opposed to each other at a predetermined interval are both DC type electrodes. Although this PDP is a DC type PDP using a linearly sequential drive scheme, a trigger electrode 45 serving as an AC type electrode all the surface of which is covered with an insulating layer is provided to decrease a discharge voltage and improve a response speed.
The trigger electrode 45 in which all the surface is flat is adhesively formed on a back glass plate BGP by thick-film printing or the like, and an insulating layer 44 is adhesively formed on the surface of the trigger electrode by thick-film printing or the like to cover the trigger electrode. The plurality of cathode electrodes 42 are adhesively formed on the insulating layer 44 by thick-film printing or the like.
Although the plurality of anode electrodes 41 are adhesively formed on a front glass plate FGP, the anode electrodes are transparent thin-film electrodes.
A plurality of barrier ribs 43 are adhesively formed on the front glass plate FGP by laminate printing of a low-melting-point glass or the like such that the barrier ribs are parallel to the anode electrodes 41.
This employs a linearly sequential drive scheme, and does not perform a memory operation. Prior to a discharge of the cathode electrodes 42, the trigger electrode 45 is set in a negative potential. Thereafter, a discharge is made between the anode electrodes 41 and the cathode electrodes 42 to accumulate positive wall charges on the insulating layer 44. When the cathode electrodes 42 are sequentially replaced and then discharged, the positive wall charges make weak discharges. This discharge serves as a trigger to make a discharge between the anode electrodes 41 and the cathode electrodes 42 as a main discharge.
In the above prior art, many studies and results about a pulse memory scheme in the DC type PDP are reported. However, the pulse memory scheme has not been realized for the following reason. That is, sputtering of the cathodes caused by impact of positive charges, i.e., ions. This is a problem shared by the DC type PDPS.
Although the conventional memory sheet type hybrid PDP shown in FIG. 1 has been invented to solve the problems of a conventional DC type PDP or an AC type PDP, there are several problems which are not solved.
For example, since there are required two electrode plates, a reduction in cost cannot be easily achieved. A large electrostatic capacity between the two memory electrodes is a disadvantage in view of driving the same.
As one form of the trigger electrode DC type PDP shown in FIG. 2, there is proposed a PDP having a metal mesh structure in which one memory sheet of the above memory sheet type PDP is used as a trigger electrode. However, since a phosphor-coated portion is limited, the luminance is low, and only a trigger operation for helping rising of a DC discharge is found out. A memory drive method using the above structure has not been invented.
As the plasma display discharge tube, in addition to the above DC type PDP, AC type PDP, and hybrid PDP, there is known a half-ADC type PDP in which one of X and Y electrodes is of an AC type and the other is of a DC type.
In order to make these PDPs color, a method of coating three primary colors, i.e., red, green, and blue phosphors on a portion near a discharge cell is used. In this case, in the DC type PDP, the phosphors are coated on the anode electrode side to avoid ion impact. However, in the AC type PDP, the X and Y electrodes receive the ion impact.
In a three-electrode AC type PDP proposed to avoid the ion impact, as shown in FIG. 3, a sustain discharge (memory discharge) is performed on the same plane, and a phosphor-coated surface is assured on the side opposing the plane, thereby reducing the problem of ion impact. This is a hybrid type PDP obtained by complexing an AC type electrode and a DC type electrode, and various PDPs of the similar type as described above are also proposed.
The three-electrode AC type PDP shown in FIG. 3 will be briefly described below. A plurality of X electrodes 53 for address are adhesively formed on a back glass plate BGP by thick-film printing or the like. In addition, a plurality of partition wall (barrier ribs) 56 are adhesively formed on the back glass plate BGP by laminate printing of a low-melting-point glass or the like to be parallel to the plurality of X electrodes 53. Red, green, and blue phosphors 57 are coated on the side surfaces of each of the X electrodes 53 and each of the barriers 56 in correspondence with the X electrodes 53. Even though the X electrodes 53 are coated with the phosphor, since the particles thereof are coarse, the electrodes operate as the DC type electrodes but not as the AC type electrodes.
A plurality of stripe-like Y electrodes 51 and a plurality of stripe-like Yc electrodes 52 which are parallel to each other are formed on a front glass plate FGP, and each of the surfaces of the electrodes are covered with an insulating layer and a protective layer formed thereon. There electrodes each operate as the AC type electrode.
The plurality of X electrodes 53 and the plurality of Y electrodes 51 cross one another to constitute an X-Y matrix electrode, and functions as an address electrode. All the Yc electrodes 52 are commonly connected to each other to carry out a memory discharge between the Yc electrodes 52 and the same.
A positive pulse voltage depending on a video signal is applied to the plurality of X electrodes 53, and a negative pulse voltage depending on a sequential scanning signal is applied to the plurality of Y electrodes 51. When a discharge occurs therebetween, a positive wall charge is accumulated on the Y electrodes 51. Thereafter, an AC pulse voltage is applied between the Y electrodes 51 and the Yc electrodes 52 to thereby perform a continuous memory discharge display.
Since the phosphor layers 57 are formed on the X electrodes 53 separated from the display discharge electrodes, such a characteristic feature that the phosphors 57 do not receive impact of ions generated by the discharge can be obtained.
As a method of driving these PDPs by a memory operation, in the DC type PDP, there is a pulse memory scheme PDP using such a phenomenon that because of the presence of metastable atoms and charged particles existing in a discharge cell space which is once discharged, a re-discharge tends to be easily produced. Further, in the AC type PDP, there is a wall-charge memory scheme which makes a re-discharge by using the difference between wall voltages generated by the so-called wall charges, i.e., charged particles accumulated on the insulating layers on the surfaces of the X and Y electrodes.
In the above conventional DC type PDP, the role of the anode electrode and the role of the cathode electrode are separated from each other. Since the anode side does not receive the ion impact, a phosphor can be coated on the anode side. However, since the anode side does not have a memory function inherently, only low luminance is obtained disadvantageously.
In the PDP using the DC type pulse memory scheme, sputtering of the cathode caused by impact of positive charges, i.e., ion impact disadvantageously made the life time of the panel short.
The AC type PDP has a characteristic feature in which a memory function can be obtained by using wall charges. However, since both the X and Y electrodes receive ion impact, a phosphor coating portion is extremely limited, and sufficient luminance and sufficient life time cannot be assured.
Since the half-AC type PDP described above has the same operation as that of the AC type PDP, the former has the same problem as that of the AC type PDP. In a three-electrode AC type PDP proposed to solve the problem, electrodes increase in number not only to prevent an increase in resolution but also to make improvements in luminance and a yield difficult.
In consideration of the above points, the present invention is to propose a plasma display discharge tube, having a long-life AC type electrode, in which an electrode structure is simplified to reduce manufacturing steps in number, and driving using a pulse memory scheme which can be conventionally realized by only a DC type plasma display discharge tube having high emission efficiency and excellent responsibility is made possible.